LED push buttons

[pros] has come up with a very elegant way of making lighted buttons (translated). Using a bunch of small push buttons harvested from old CD players, he rigged this unique way of mounting LEDs. Each LED has two buttons under it. They are wired in parallel, so if either of them is pushed, the button works. The LED isn’t actually soldered where it passes through the board. The anode and cathode are bent around and soldered to allow the LED a little bit of travel. There’s a good picture of how he did this on the site. The rest of the details might be hard to decipher though, it looks to be in dutch.

rasz: I can only assume you don’t have a degree in mechanical engineering, so I won’t blame you for a little ignorance.

LED legs are usually made (mostly) of iron, and iron is one of the materials that has a so-called “fatigue limit”, unlike, for example, aluminium.
If you stay below this stress level, the material will never fail due to metal fatigue. This is called the infinite life concept.

Now I don’t feel like calculating the stresses in the legs of the LEDs, but with a very small travel (say, 2mm) and the length and shape of the legs in this example, I think they are well below the fatigue limit.

IMHO, after looking at the picture, those LED’s should hold up nicely with the little amount of movement that they will be traveling. They have enough room to move and not have any stress, although i would make sure that the ends are soldered down well enough so that the solder point doesn’t break off if it is a cold solder

Looking at those initially I thought that they were being used like a two-way momentary rocket switch, so pushing the LED up a tad would push one switch, and down, the other…
Evidently not, but I’m sure as hell going to try doing that!

As a fellow ME, I can soundly agree with what Sparky said above. However, for you nay-sayers, you could easily modify this by making a sharper bend in the led leads immediately upon it passing through the board, thus preventing the led from moving far away from the buttons. Then, instead of using the remaining leads from the LED to connect to the solder point, you simply use a small length of thin wire. This setup would still function properly with no fear of stress on the solder point, although the LED might jiggle around more than you want.

Funny how people are so alarmist about metal fatigue then as a solution suggest wires, and what are wires? Thin strands of.. -that’s right- metal.

Incidentally the patent office must have thousands of ways to connect those LED, which nicely gives me an excuse to share this interesting yet deceivingly simple link:http://www.google.com/patents
Be careful though, it’s a link that can really engross some people and before you know it an hour has passed.

Oh and of course there are ready-made buttons with LED, so this projects is designed to do it on the cheap for people on a low budget, and thinking up expensive fixes is defeating the purpose.

there has been extensive ‘research’ on this and other methods over at midibox.org, with a variation of this method coming in over two years ago.
If I remember right, the led leads were bent out, and the led base was epoxied to the button cap, making one unit. wires connected the leads to the pcb. on a midibox, the dout is usually NOT built onto the interface panel, and all of those leds have to be individually wired to the dout board anyway, so fatigue is not much of an issue.

The button caps were taller, such that there was room to cut a notch on top to let the leads out of the sides.

anyway, if you are in need of button making ideas, there is several over there.. check it out.

I realise that, but I just think the feeling the pins will break in the configuration the guy uses is a bit panicky, and just as wire although it’s metal is pretty bend-proof so I expect is the setup with loops combined with the short traveldistance, but I guess only trial and error can tell, and it’s dependant, how many hundred times you can press it, on the material of the pins of the LED, which I don’t think are always the exact same composition amongst various manufacturers, at least that is my impression from the LED I’ve seen, sometimes the leads seem slightly different in composition to me, but I might be imagining things.

I think the LEDs will survive about a gazillion presses. The displacement is about a mm, or less (depends on how far you have to press the underlying buttons). This millimeter is spread over 3 cm of LED legs. I doubt it will ever break.
Nonetheless, the physics behind metal fatigue are interesting, but that isn’t what this hack is about.